Global climate change — AQA GCSE Combined Science
Test yourself on Global climate change with AQA GCSE practice questions.
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Global climate change explained
Average global temperature is calculated from many weather stations, ocean buoys and satellite measurements over long periods.
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When this average rises, the extra thermal energy drives a chain of effects: ice sheets and glaciers melt, sea levels rise, and warmer oceans and air alter evaporation, rainfall patterns and storm behaviour. These shifts in long-term weather patterns are what scientists call climate change. The temperature rise is therefore treated as a major cause because it supplies the energy and the melting that produce the wider changes. A single hot summer is weather, not climate; evidence comes from decades of data and from patterns across the whole planet.
There are several potential effects of global climate change.
Global climate change is the long-term shift in average weather patterns across the Earth, driven mainly by increased greenhouse gases such as carbon dioxide and methane. Its potential effects are varied and interconnected. Rising global temperatures melt ice sheets and glaciers, adding water to oceans, while warmer water expands, so sea levels rise and low-lying coasts flood. Weather may become more extreme: heatwaves, droughts, storms and heavy rainfall occur more often. Habitats shift, so some species move towards the poles or to higher ground, while others cannot and face extinction. Crop yields may fall where drought and heat stress plants, threatening food security. Human health is affected by heat stress and changing ranges of disease-carrying insects. These effects are potential because their size and timing depend on future emissions and on how natural systems respond.
describe briefly four potential effects of global climate change
Global climate change is the long-term shift in average weather patterns, driven mainly by increased greenhouse gases such as carbon dioxide and methane. Its effects are wide-ranging and interconnected. Four commonly described effects are: rising sea levels, as land ice melts and ocean water expands when warmed; more frequent and severe extreme weather, including heatwaves, droughts, storms and heavy rainfall; changes to ecosystems and species distribution, as organisms migrate or decline when their habitats become unsuitable; and impacts on human agriculture and water supply, as changing rainfall and temperatures reduce crop yields and freshwater availability. These effects are potential because the exact scale depends on future emission pathways, but the direction of change is well supported by evidence.
discuss the scale, risk and environmental implications of global climate change.
Discussing global climate change means considering how large its effects are, how likely and serious the risks are, and what the consequences are for the environment. Scale refers to the size and reach of change: it is global, long-term and affects atmosphere, oceans, ice, land and living things. Risk combines the probability of a harmful outcome with its severity; for example, a small rise in sea level may be manageable in some places but catastrophic for low-lying islands. Environmental implications include loss of biodiversity, altered habitats, ocean acidification, disrupted food chains and changes to water and nutrient cycles. A good discussion weighs evidence, recognises uncertainty in future projections, and considers both environmental and human consequences.
Your focus
- State that average global temperature is a long-term global mean derived from many measurements.
- Explain how a rise in average global temperature leads to melting ice, sea level rise and changed weather patterns.
- Distinguish between a weather event and a change in climate using the idea of long-term patterns.
Show all 12 objectives
- State that global climate change has several potential effects.
- Describe at least two effects on the environment or people.
- Explain how one effect results from rising global temperatures.
- State four potential effects of global climate change.
- Explain the mechanism linking each effect to global warming.
- Distinguish between climate change effects and their causes.
- Explain the scale of global climate change in space and time.
- Evaluate risk by combining likelihood and severity of effects.
- Analyse environmental implications and distinguish mitigation from adaptation.
Global climate change exam tips
Marking Points
- Average global temperature is a long-term mean calculated from worldwide measurements, not the temperature of one place or one day.
- A rise in this average adds thermal energy to the Earth system, melting ice and expanding ocean water so sea levels rise.
- Warmer air and oceans change evaporation and precipitation, shifting rainfall patterns and the frequency or intensity of some extreme weather.
- Climate change means a sustained shift in long-term weather patterns, so the temperature rise is a major cause rather than a single weather event.
- Evidence for the trend comes from comparing many decades of data from multiple sources, which reduces the effect of local variation.
- Identify that global climate change is a long-term change in average weather patterns, not a single weather event.
- Describe at least two distinct effects, such as sea level rise from melting ice and thermal expansion of seawater.
- Explain how one effect links to a cause, for example higher temperatures melting ice sheets and glaciers.
- Recognise that effects are potential and depend on future greenhouse gas emissions and natural feedbacks.
- Give a consequence for living organisms, such as habitat loss, changed species distribution or reduced crop yield.
- Use correct terms such as greenhouse gas, sea level, habitat and extinction.
- Rising sea levels caused by melting land ice and thermal expansion of ocean water, threatening low-lying coasts and islands.
- More frequent or intense extreme weather, such as heatwaves, droughts, storms and heavy rainfall, affecting people and infrastructure.
- Changes to ecosystems and species distribution, including migration, reduced biodiversity and possible extinction where organisms cannot adapt or move.
- Reduced agricultural productivity and water availability, leading to food and water insecurity in some regions.
- Additional valid effects such as ocean acidification, spread of disease vectors, or damage to coral reefs, if briefly described.
- Scale: climate change is global and long-term, affecting the atmosphere, oceans, ice sheets, land and ecosystems worldwide.
- Risk: risk depends on both the likelihood of a hazard and the seriousness of its consequences, so the same change can pose different risks in different places.
- Environmental implications: loss of biodiversity, habitat change, ocean acidification, disrupted food chains and altered water and nutrient cycles.
- Human and economic implications: threats to food security, water supply, coastal settlements, health and infrastructure.
- Uncertainty and evidence: projections vary with future emission scenarios, so discussion should acknowledge ranges and confidence rather than treating all outcomes as certain.
- Mitigation and adaptation: reducing emissions lowers future risk, while adaptation manages effects that are already unavoidable.
Examiner Tips
- 💡Define average global temperature before explaining its effects, so your answer shows the term is understood.
- 💡Use a cause-and-effect chain such as warmer average temperature → ice melt and thermal expansion → sea level rise.
- 💡Quote the idea of long-term patterns when distinguishing climate change from a one-off weather event.
- 💡Read the command word: 'describe' needs effects, while 'explain' needs a cause-and-effect link.
- 💡Use named examples, such as melting of polar ice or drought reducing crop growth, to make answers concrete.
- 💡Link each effect back to a cause, such as increased greenhouse gases trapping more energy.
- 💡Read the command word 'describe briefly' and give four distinct effects, each with a short explanation of how it arises.
- 💡Use precise terms such as 'thermal expansion', 'biodiversity' and 'food security' to show secure understanding.
- 💡Link each effect to a mechanism where possible, for example melting ice and thermal expansion both raise sea level.
- 💡Keep each point concise; four clear effects are better than one long, detailed paragraph.
- 💡Use the command word 'discuss' to present balanced points, including both evidence and uncertainty.
- 💡Structure your answer around the three prompts: scale, risk and environmental implications, so every part is addressed.
- 💡Support points with specific examples, such as low-lying islands for sea-level risk or coral reefs for ocean acidification.
- 💡Use comparative language such as 'greater risk', 'more severe' and 'less certain' to show judgement rather than listing facts.
Common Mistakes
- Confusing weather with climate: correction — weather is short-term and local, while climate is the long-term pattern over decades.
- Saying the temperature rise is the only cause of climate change: correction — it is a major cause, and other factors such as changes in greenhouse gas concentrations also contribute.
- Treating one cold winter as proof that global warming is not happening: correction — a single season is weather and does not overturn a long-term global trend.
- Confusing weather with climate: a cold winter does not disprove climate change. Correction: climate is the long-term average, so judge trends over decades.
- Thinking only polar bears are affected. Correction: describe wider impacts on habitats, food production and human health.
- Stating that sea level rise is only from melting ice. Correction: thermal expansion of warmer water also raises sea level.
- Confusing weather with climate: weather is short-term and local, while climate is long-term and regional or global. Correction: describe effects as long-term changes in average conditions or patterns.
- Claiming that all effects are certain and identical everywhere. Correction: describe them as potential effects whose severity depends on future emissions and local conditions.
- Listing a cause rather than an effect, such as 'burning fossil fuels releases carbon dioxide'. Correction: state the consequence, for example 'sea levels rise as ice melts'.
- Treating 'scale' as only geographical size and ignoring timescale. Correction: scale includes both spatial extent and the long duration of change.
- Confusing risk with hazard. Correction: risk is the chance of harm combined with how serious that harm would be, not simply the existence of a hazard.
- Assuming all environmental effects are reversible. Correction: some effects, such as species extinction, are permanent on human timescales.